This invention relates generally to systems and methods for screening incoming telephone calls and, more specifically, to techniques for selectively screening calls in the context of cellular telephony.
Various techniques have been developed which enable the telephone subscriber to screen incoming calls. For example, a telephone answering machine may be activated to answer all incoming telephone calls, to even in the presence of the called party. However, this technique is not preferred because callers may hand up immediately after hearing the called party's prerecorded message, on the assumption that the called party is not present. Furthermore, a connection is made between the calling and the called party, regardless of the caws origin or the calling party's status.
Another prior art technique for call screening is known as "caller ID". With the advent of the "caller ID" feature, telephone subscribers can identify callers through a display that is activated during the ringing interval and which displays the number of the calling party. The subscriber has the option of not answering,, the call, and typically uses the displayed information to determine his or her actions. However, one disadvantage of using "caller ID" to screen incoming calls is that the phone still rings when undesired calls come in, thereby annoying the subscriber.
Existing call screening techniques are ineffective in the environment of a typical cellular telephone system, because subscribers are billed for incoming answered calls, as well as for outgoing calls. Moreover, state-of the-art cellular systems do not even provide the "caller ID" feature. If the system subscriber receives a sufficient number of incoming calls, the subscriber's cellular phone bill may increase substantially. Unfortunately, the subscriber does not have control over the receipt of incoming telephone calls, short of leaving the telephone off-hook or letting the phone ring repeatedly. And, as if to add insult to injury, many of these incoming calls are undesired. This is a particularly problematic situation due to the recent proliferation of telemarketing schemes.